Cisco router's boot sequence, WHEN at
boot time, messages are deciphered, WHERE
console connection to actual router;

Cisco router's learning steps are:

login to a router via console port connector;

the router's initial configuration byusing Initial Configuration Dialog software interface, and
then the router's manual configuration
because at the initial configuration stage the router was non-configured
without commands
is non-configured;

the router's self identification by its router settings; After the
router's manual configuration, settings are clock rate, bandwidth, each IP
address for each network interface, passwords, ... ; After manual
configuration is loaded, and then do System Configuration Dialog
software interface;
Changing/editing/modifying startup configuration file, and understanding between
cold boot and warm boot WHEN copy; Configuring global parameters such as

by allowing override static routers, the usage "dynamic" begins; To do
so, allow dynamic routes; TCP/IP subnets knowledge is
required because defined default gateway by WHOM should be
unique regardless of whether global OR local OR remote OR ... ;

TCP/IP; Also see:
Protocol and Port; TCP/IP address
calculation by converting from decimal to binary, and knowing of each default
gateway address for each TCP/IP address, and then subnets by masking
subnet a.k.a. subnet masking;